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#197742 - 12/17/10 05:32 PM 3 phase inverter
bwise121 Offline
Member
Registered: 09/11/03
Posts: 114
Loc: Sacramento, CA USA
I've been asked to help facilitate the installation of a 10 kw 3 phase commercial pv system. There are some budget concerns. The inverters that we've looked at are quite expensive and are hoping there is a work around.
1. Can we use a single phase pv system that backfeeds the 3 phase main panel?

2. Can we use 3 single phase pv inverters and wire it in such a way that it is essentially the same as a 3 phase inverter? (someone told me you can)

I'm open to other suggestions.

Thanks,
Byron
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#197746 - 12/17/10 07:39 PM Re: 3 phase inverter [Re: bwise121]
HotLine1 Offline


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Registered: 04/03/02
Posts: 6776
Loc: Brick, NJ USA
Byron:
My opinions...

1: I strongly doubt that the POCO would allow you to grid-tie single into 3 phase.

2: I have not seen any attempt to do this. Theoreticaly it sounds feasible, like using three single phase transformers in lieu of a three phase transformer. Also, you may have issues with the AHJ, unless you can provide documentation (Mfg) of approved/listed use.



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#197773 - 12/18/10 06:42 PM Re: 3 phase inverter [Re: bwise121]
LarryC Offline
Member
Registered: 07/05/04
Posts: 780
Loc: Winchester, NH, US
What drove the decision that the system had to be 3 phase?

10 KW is a relatively small system. What size service are you looking to tie into?

Are there significant single phase loads off of the 3 phase service?
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#197789 - 12/19/10 10:51 AM Re: 3 phase inverter [Re: LarryC]
sparkyinak Offline
Member
Registered: 07/08/07
Posts: 1307
Loc: Alaska
Many of the single phase inverters I dealt with can be wired as three phase. The problem is you are limited limited to one inverter per leg. Pending on the model, you could achieve 10kW. You won't be able to "stack" inverter so you would not be able to expand on it in the future if that was a future plan. Also as hotline1 mention, check with the POCO to see the system you plan to use is allowed to be grid tied
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#197835 - 12/22/10 02:38 PM Re: 3 phase inverter [Re: LarryC]
bwise121 Offline
Member
Registered: 09/11/03
Posts: 114
Loc: Sacramento, CA USA
The service main is 600A 120/208 and there is one 225A 3phase, and two 100A single phase. Plenty of room for a small PV system.

Thanks!
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#197851 - 12/23/10 04:38 PM Re: 3 phase inverter [Re: bwise121]
LarryC Offline
Member
Registered: 07/05/04
Posts: 780
Loc: Winchester, NH, US
Originally Posted By bwise121
The service main is 600A 120/208 and there is one 225A 3phase, and two 100A single phase.


Assuming the 225A and 100A are designating sub panels off of the service, I would connect the inverter to the same PHASE as either one of the single phase panels. When the inverter is putting out current, it will help offset the unbalanced load.
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#198216 - 01/15/11 08:07 PM Re: 3 phase inverter [Re: LarryC]
moreDER Offline
New Member
Registered: 01/15/11
Posts: 1
Loc: WA
The AHJ and the POCO would want a net metering set up, I'm pretty sure. So a separate production meter and all the signage and disconnects (lockable, window) etc. -

One idea would be to use the DC power for loads that want DC - computers, chargers, LED lighting (do a retrofit), DC motors, DC Thermal Heaters, etc. Transforming DC to AC to DC again is inefficient.

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#198249 - 01/16/11 08:38 PM Re: 3 phase inverter [Re: bwise121]
Trumpy Offline


Member
Registered: 07/05/02
Posts: 8211
Loc: SI,New Zealand
Originally Posted By bwise121
I've been asked to help facilitate the installation of a 10 kw 3 phase commercial pv system. There are some budget concerns.

Byron,
Who designed this system, if it was eventually found that it couldn't be done with the capital available?
That is the keystone of any business venture, the brief to the system designer would (or should have been) do this with X$$$$$$, that is your starting point in any project.
Asking the technical staff to make compromises on the basis of lack of funds is not the best start to any project, no matter how large or small. crazy
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#198268 - 01/17/11 08:31 AM Re: 3 phase inverter [Re: moreDER]
PAteenlectrician Offline
Member
Registered: 01/06/11
Posts: 64
Loc: Cressona, Pa, U.S.A. (Schuylki...
Originally Posted By moreDER
One idea would be to use the DC power for loads that want DC - computers, chargers, LED lighting (do a retrofit), DC motors, DC Thermal Heaters, etc. Transforming DC to AC to DC again is inefficient.


That would still cost alot of money.
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